Methods for Delivery and Distribution of Amendments for Subsurface Remediation: A Critical Review

The ability to reliably deliver and widely distribute remedial amendments through the subsurface environment is of paramount importance to achieve cleanup objectives for contaminated sediments and groundwater for protection of sensitive environmental habitats and natural resources. A wide range of amendments, delivery techniques, and subsurface access methods are available. However, the applicability of these approaches is dependent on a multitude of site‐specific factors. In this review, an overview of amendments and access/distribution methods is provided, along with discussion of the maturity level, advantages, and limitations that relate to the potential effectiveness of each approach in the context of site‐specific factors. Each amendment and delivery approach are further evaluated for applicability to the following subsurface target zones: saturated, unsaturated, and perched water, with specific focus on high and low permeability regions in each zone. The review highlights a critical need for field‐tested approaches targeting unsaturated and perched water zones, as well as low‐permeability regions within all subsurface regions. The intent of this review is to provide critical information and insight into how amendments can be delivered, emplaced, and/or distributed effectively in the subsurface environment to effectively manage subsurface contamination.